This invention relates to a method and a device for cutting braking surfaces of a brake rotor mounted on a wheel-mounting flange of a wheel bearing assembly.
Among wheel bearing assemblies, there are ones for driving wheels and ones for non-driving wheels. FIG. 3 shows one example. This wheel bearing assembly is for a driving wheel, and comprises an outer member 1, an inner member 2 and double-row rolling elements 3 mounted between the outer and inner members 1 and 2.
A vehicle body-mounting flange 4 is formed on outer periphery of the outer member 1, and double-row raceways 5 are formed on an inner periphery of the outer member.
The inner member 2 comprises a hub ring 2a as a first rotary member and a raceway member 2b as a second rotary member. On an outer periphery of the hub ring 2a, a wheel-mounting flange 6 and a raceway 7, opposing one of raceways 5 formed on the outer member 1, are formed. Hub bolts 8 are provided on the wheel-mounting flange 6. A wheel pilot 9 is formed at one end of the hub ring 2a, while a small-diameter portion 10 is provided at another end of the hub ring. A spline hole 11 extends through the hub ring 2a from its small-diameter portion 10 to a bottom of the wheel pilot 9.
The raceway member 2b is fitted on the small-diameter portion 10 of the hub ring 2a, and is formed on its outer periphery with a raceway 12 opposing the other of the double-row raceways 5 formed on the outer member 1.
The double-row rolling elements 3 are mounted between the double-row raceways 5 formed on the inner periphery of the outer member 1 and the raceways 7 and 12 formed on the hub ring 2a and the raceway member 2b, respectively, to support the inner member 2 rotatably relative to the outer member 1. Also, seals S are mounted at both ends of a space between opposing surfaces of the outer member 1 and the inner member 2 to prevent entry of dust into the space.
With the wheel bearing assembly having the above structure, in mounting to a vehicle, the vehicle body-mounting flange 4 formed on the outer member 1 is mounted to a vehicle body by tightening bolts.
Also, a spline shaft provided on an outer joint member of a constant-velocity joint is inserted into the spline hole 11 formed in the hub ring 2a, a nut is brought into threaded engagement with a threaded shaft formed at a tip of the spline shaft, and the nut is tightened with a predetermined torque to press the hub ring 2a and the raceway member 2b against each other so as to impart a preload between the rolling elements and the raceways 5, 7 and 12.
Further, wheel nuts 14 are threaded onto the hub bolts 8 provided on the wheel-mounting flange 6, and these nuts are tightened to mount a brake rotor 13 and vehicle wheel to the wheel-mounting flange 6.
With such a wheel bearing assembly, because run-out of a braking surface 13a during rotation of the brake rotor 13 can be a cause of brake-judder during braking, high machining accuracy and high dimensional accuracy are required for parts of the wheel bearing assembly.
But even if machining accuracy of each part is increased, because machining errors of respective parts accumulate during assembly of the wheel bearing assembly, and also because assembling errors develop, it is impossible to suppress run-out of the braking surface 13a of the brake rotor 13.
In order to solve this problem, a cutting method has already been proposed in which a wheel bearing assembly is assembled so as to be actually mountable, and a wheel bearing assembly with a brake rotor mounted to a wheel-mounting flange 6 provided on inner member 2 is mounted on a cutting machine, and braking surface 13a of brake rotor 13 is cut while rotating the inner member 2 and the brake rotor 13 (Japanese patent publication 11-19803).
According to this cutting method, since the braking surface 13a of the brake rotor 13 is cut with the wheel bearing assembly, with the brake rotor, in an actually mounted state, accumulated errors in which machining errors of respective parts accumulate, and strains produced in mounting the brake rotor 13 are removed. Thus, by mounting the wheel bearing assembly with the brake rotor thus cut on an actual vehicle, the wheel bearing assembly is restored to a state at the end of cutting, so that run-out of the braking surface 13a during rotation of the brake rotor 13 is extremely small. Thus, it is possible to rotate the brake rotor 13 with extremely high accuracy.
In the above method, in which the braking surfaces 13a of the brake rotor 13 are cut in an actual mounted state, a spline shaft provided at a tip of a drive shaft is inserted into a spline hole 11 formed in the inner member 2, a preload nut is threaded onto a threaded shaft provided at a tip of the spline shaft, and the pre-load nut is tightened to make the wheel bearing assembly be in an actual mounted state. Thus, attaching and detaching the wheel bearing assembly with the brake rotor are extremely troublesome, and it takes a long time to perform cutting.
An object of this invention is to provide a method for cutting braking surfaces of a brake rotor of a wheel bearing assembly which makes it possible to efficiently cut braking surfaces of the brake rotor in a short time by making it possible to easily put the wheel bearing assembly in an actual mounted state. Another object of the invention is to provide a device for practicing the method.
According to this invention, there is provided a method of cutting braking surfaces of a brake rotor of a wheel bearing assembly. The wheel bearing assembly comprises an outer member having a vehicle body-mounting flange on its outer periphery, an inner member having a wheel-mounting flange on its outer periphery, rolling elements disposed between the outer member and the inner member for rotatably supporting the inner member, and the brake rotor which is mounted to the wheel-mounting flange of the inner member. The method comprises the steps of assembling the wheel bearing assembly with the brake rotor in an actual mounted state, determining a mounting surface of the vehicle body-mounting flange to be mounted on a vehicle body as a reference surface, non-rotatably supporting the outer member positioned against the reference surface, clamping the inner member with a pair of oppositely arranged pressing members from both ends thereof with a pressing force corresponding to a clamping force in the actual mounted state, rotating the inner member and the brake rotor while maintaining a clamped state, and cutting the braking surfaces of the brake rotor by moving a cutting tool in a direction parallel to the reference surface.
With this arrangement, since the wheel bearing assembly with the brake rotor can be brought into an actual mounted state by non-rotatably supporting the outer member while positioning it against the reference surface on the vehicle body-mounting flange formed on the outer member, and pressing the inner member with a pair of pressing devices from both axial ends of the inner member, it is possible to efficiently perform cutting of the braking surfaces of the brake rotor.
By performing dry-cutting, with no cutting liquid, for cutting the braking surfaces by the cutting tool, and cutting the braking surfaces of the brake rotor while supplying compressed air from one end of the outer member so that the compressed air flows along an outer periphery of the outer member, it is possible to prevent chips produced by cutting from adhering to seals of the wheel bearing assembly and thus avoid damage to the seals.
Also, by performing cutting of the braking surfaces while sucking chips, it is possible to reliably prevent chips from adhering to the seals of the wheel bearing assembly and thus avoid damage to the seals, and also to prevent scattering of chips to a surrounding environment.
According to this invention, there is also provided a cutting device for cutting braking surfaces of a brake rotor mounted on a wheel bearing assembly. The wheel bearing assembly comprises an outer member having a vehicle body-mounting flange on its outer periphery. The vehicle body-mounting flange has a mounting surface to be mounted to a vehicle body, which mounting surface is to be used as a reference surface. The wheel bearing assembly also comprises an inner member having a wheel-mounting flange on its outer periphery, and rolling elements disposed between the outer member and the inner member. The cutting device comprises a positioning member for positioning the reference surface on the vehicle body-mounting flange of the outer member, a chuck device for clamping the outer member, a pair of pressing devices for pressing and clamping the inner member from both ends thereof with a pressing force corresponding to a clamping force in an actual mounted state, a rotary device for rotating the inner member, and a tool rest carrying a cutting tool for cutting braking surfaces of a brake rotor and mounted so as to be movable in a direction.parallel to the reference surface on the vehicle body-mounting flange of the outer member.
With this arrangement, by clamping the outer member with the chuck device with the reference surface of the vehicle body-mounting flange provided on the outer member in abutment with a positioning member, and pressing the inner member with a pair of pressing devices from both sides thereof, it is possible to put the wheel bearing assembly with the brake rotor in an actual mounted state. And, by rotating the inner member via a rotary device and radially inwardly moving the tool rest from an outer periphery of the brake rotor, it is possible to cut the braking surfaces of the brake rotor.
Since a cutting tool comprises a pair of tool holders each carrying a cutter for cutting the braking surfaces, by fixing one of the tool holders relative to the cutter rest while supporting the other tool holder so as to be openable and closable relative to the one tool holder, a distance between the cutters can be adjusted. Thus, it is possible to arbitrarily adjust an amount of cut into the braking surfaces of the brake rotor. Also, because after cutting of the braking surfaces, the cutting tool can be returned to an original position at a start of machining with the other tool holder open relative to the one tool holder, it is possible to prevent damage to the braking surfaces of the brake rotor subjected to cutting.
By providing the cutting device according to this invention with an air supply device for supplying compressed air from one end of the outer member along its outer periphery, or a suction device for sucking and removing chips formed by cutting, it is possible to solve a problem in which cutting powder or chips adhere to the seals of the wheel bearing assembly and imparts damage to the seals.